sorry bit of a disgusting one here.....

[welshandproud]

Discoloured, rotten, crumbling toe nails.Does anyone have any experience and is there a treatment/cure?

It sounds like a fungal infection, you are best off seeing your GP.

Yup, sounds fungal and it can usually be sorted out, but it may take a new nail to grow through before it looks nice again. See your GP - not something you can self medicate terribly well.